Patent Publication (1) discloses a method for forming a buildup layer on a core substrate having a conductive region and an insulative region. In Patent Publication (1), by oxidizing portions of aluminum, a core substrate is formed with aluminum (conductive region) and aluminum oxide (insulative region). In addition, Patent Publication (1) discloses that the insulative region of Patent Publication (1) is made up of a porous region and a non-porous region, and that the porous layer provides non-conductive features and the denser region works as a barrier layer which prevents the conductive region from being oxidized.
[Prior Art Publication]
[Patent Publication]
[Patent Publication 1] U.S. Pat. No. 6,899,815 B2